Since 2010 Gmail has been making statements and trying to improve user acceptance of the encrypted Gmail access but with the open option left to the users to either use it or not, but today Google has made it mandatory for all the Gmail users to have their Gmail communication only over HTTPS secure communication protocol.
This comes mostly as a response to some of the recent events like the government snooping into the servers and its secretive PRISM program, NSA’s Acceptance on the issue, and public disclosure by NSA contractor Edward Snowden about Government Surveillance.
The present setup now allows the mail flow from the sender to the receiver in a completely encrypted manner, the mailing starts on a secure HTTPS page, reaches the Google Servers, flows between the Google servers and datacenters on highly encrypted basis then sent out to other servers or the receiver with the encryption intact.
All this said is still not Government or NSA proof which would eventually find way and means to eavesdrop or send out the National Security Letter under Foreign Intelligence Surveillance Act demanding client records, Google received 20000 to 22000 just in 2012.
But the latest move would at the moment protect the integrity and authenticity of the content of the mails of the users and would deter most other snoopers and hackers around from getting access to your mails. Though this could have been implemented some years ago, and still most Email providers are just being lethargic to implement.